[NT/RBRC seminar] Infrared structure of QED as a many-body theory of worldlines

by Xabier Feal

Friday 18 Mar 2022, 09:00 → 11:00 US/Eastern

https://bnl.zoomgov.com/j/1611743505?pwd=VTA5b3lkdDJ1UE15VklrNGtUOHdzdz09

We present a complete reformulation of QED in which matter and gauge fields are integrated out explicitly, resulting in a many-body theory of 0+1 dimensional worldlines describing spinning charges interacting through the Lorentz forces. This powerful, string inspired definition of amplitudes to all loop orders can be interpreted as a more general formulation of Wilson loops and lines, with dynamical fields and spin precession exponentiated, and contour averages exactly defined through path integrals. We then take advantage of this Lorentz covariant formulation of the interactions to examine the asymptotic behavior of QED. 

We will find that S-matrix elements, when expressed as worldlines, can be constructed to be manifestly free of soft singularities, with IR divergences captured and removed by endpoint photon exchanges at infinity that exactly match the soft coherent dressings of the Dyson S-matrix proposed by Faddeev and Kulish.  We discuss these IR structures and make connection with soft theorems, the Abelian exponentiation of IR divergences and the cusp anomalous dimension.